Abstract

Carboxylated multi-walled carbon nanotubes (MWCNT-COOH) were prepared by treating multiwalled carbon nanotubes (MWCNT) with concentrated sulfuric acid (H2SO4) and concentrated nitric acid (HNO3) at a volume ratio of 3:1. Afterwards, taking MWCNT-COOH as the modified materials and aziridine (AZ) as the cross-linking agents were added to polyether-based waterborne polyurethane (WPU) thus preparing waterborne polyurethane modified by cross-linking of aziridine/carboxylated multi-walled carbon nanotubes (AZ-MWCNT-COOH-WPU) emulsion and films. The latter was applied to the surface treatment of natural leather and synthetic leather and other coating materials. The effects of different AZ contents on the water resistance and mechanical properties of AZ-MWCNTCOOH- WPU films were analysed and are discussed. The synthesised product was characterised by FTIR, XRD, SEM and other detection methods. The results showed that AZ successfully grafted MWCNT-COOH to the molecular chain of WPU and, when the content of AZ increased, the tensile strength of AZ-MWCNT-COOH-WPU film increased, firstly from 14.8MPa to 21.8MPa and then decreased to 12.1MPa. Elongation at break decreased from 570.2% to 198.4%, the water absorption decreased from 108.9% to 2.4% thus the water resistance was enhanced.